This invention relates to an improvement in the processing of starch by the addition of specific cationic polymers to starch slurries containing swollen starch granules in order to improve the dewatering of the slurry and thereby increase production rate and yield.
When starch is derivatized with one or more reagents or degraded with acid or oxidizers or when it is exposed to alkali or subjected to a combination of these treatments, some of the granules become swollen or partially gelatinized. The presence of these swollen starch granules in the treated starch product reduces dewatering and drying rates and requires increased energy for drying. Moreover, when the treated starch is washed in a continuous centrifugal device such as a Merco the swollen starch granules are removed along with the reaction by-products due to their reduced density with respect to the intact granules. In these cases, while the processing rates are improved by the removal of some of the swollen starch, their removal reduces product yield and also contributes to increased effluent load.
Several synthetic polymers have been proposed as dewatering aids in washing such treated starch products however none to date have showed significant improvement in yields and processing rates when employed on a commercial scale.
It is therefore an object of the present invention to provide a method for washing treated starch containing swollen starch granules in order to maintain high processing rates without reducing the yield or increasing the effluent level.